Invasive lionfish harming Caribbean reefs

The spectacularly beautiful lionfish with its undulating venomous spines is quite the sight to see, but its invasion of Caribbean coral reefs may pose a very serious threat. For the past five years or so, I have been reading about the population explosion of lionfish in the Caribbean. However, the magnitude of the problem did not strike home until a recent dive trip to the Bahamas. I was surprised to see how common they had become and many divers (professional lobster and sponge divers) told me they had seen a huge increase in abundance in just the last 1-2 years. The lionfish invasion in the North Western Atlantic and Caribbean represents one of the most rapid marine finfish invasions in history.

Lionfish are not native to the Caribbean and until recently, these were only found in the Pacific and Indian Oceans. They were documented in southeast Florida beginning in 1992. Since then, they have been reported from south Florida to North Carolina and throughout much of the Caribbean. A recent study found a tenfold increase in abundance in some areas from 2004 to 2008.

How did they get here?They were probably introduced from local aquariums or fish hobbyists. One popular story mentions that Hurricane Andrew resulted in the inadvertent release of lionfish when homes and aquariums were flooded. It is thought that hobbyist release the fish rather than kill them when they grow too large or the fish hobbyist moves on to other interests. Lionfish are a popular and spectacular aquarium fish (8,000 are annually imported to the Tampa Bay area alone). By-the-way, releasing non-native animals into the wild is against Florida law and can result in a $1,000 fine or a year in jail.

So what?The predatory lionfish are voracious eaters. A study conducted by an Oregon State University scientist found that within a short period after the entry of lionfish into an area, the survival of other reef fish is slashed by about 80%. Many species were affected, including cardinal fish, parrot fish, damselfish and others. Research in the Bahamas has documented consumption of juvenile economically important fish. Therefore, the potential to upset the natural balance of coral reef ecosystems is very real.

Evidently the lionfish’s venomous spines are an impressive defense and I was unable to find much information on what critters eat lionfish. They are considered a top level predator with few if any enemies. Lionfish have been reported in the stomachs of large grouper, but laboratory behavioral experiments suggest that groupers actively avoid lionfish. Given the observed population explosion in the Caribbean, it appears that natural population control factors have not yet come into play. Although data is limited and it is difficult to accurately count them because of their cryptic nature, lionfish densities in the Bahamas are more than eight times higher than estimates from their native range.

What can be done to control lionfish populations?This is indeed a very difficult question to answer. In some areas, dive shops and clubs have organized “Lionfish Rodeos” where divers take on the mission of searching for and destroying lionfish. Throughout the Caribbean anglers and divers are encouraged to destroy any lionfish they encounter. In fact, the consumption of lionfish is now being promoted. They are reported to be delicious table fare. The venom is only found in the dorsal spines, not in the flesh. Also, cooking destroys the toxin so there is no danger in eating the flesh. The first question that comes to my mind was “how do you safely clean a lionfish?”The short answer is: very carefully!However, there are brochures on cleaning and it appears that when the fish is dead it is fairly easy to remove the dorsal spines. Although NOAA researchers have developed techniques to trap lionfish from deeper waters and larger areas that are impractical for diver removal, these measures will fail to completely eliminate lionfish. The only hope is that these measures can somewhat control abundance in some areas.

Some additional lionfish biology: Females release two buoyant egg masses that are fertilized by the male as they ascend to the surface. The eggs hatch after about two days. The larval stage probably last 30-45 days, during which they are distributed far and wide. Lionfish collected off North Carolina and the Bahamas suggests that lionfish are reproducing during all seasons of the year.

I mentioned that lionfish can be voracious feeders. It has been reported that they can expand their stomachs 30 fold when consuming a large meal. This suggests they are capable of long-term fasting and they can survive starvation for over 12 weeks.

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